The Achaemenid empire of Persia reached the Indus Valley in the fifth centrury B.C., bringing with it the Aramaic script, from which derive both the northern and southern Indian alphabets.
SUBJECT: The Achaemenid empire of Persia
Direct Object: the Indus Valley
PARTICIPLE CLAUSE MODIFYING THE SUBJECT: bringing with it the Aramaic script
Now I'm confused by "from which derive both the northern and southern Indian alphabets." I know 'which' functions as the object of the preposition 'from' but since you cannot have a prepositional phrase as a subject (see examples 1 and 2 below), isn't the verb 'derive' lacking a subject? How does this construction work?
1. Jeff know Chuck, with whom he went to school.
Here "with whom" is not the subject, but "he" is the subject.
2. They are both staying in that building, which is the tallest building on campus.
Here "which" is the subject.